Project Summary American Indian and Alaska Native (AIAN) adults are more likely to develop cancer and die from it than white American adults, reflecting pronounced and persistent cancer health disparities (CHDs). Colorectal cancer (CRC) rates are disproportionately high among AIANs in the Northern Plains and Alaska regions; likewise, risk factors for CRC are also high, including non-modifiable factors such as increasing age and rurality, and proven modifiable risk factors such as physical inactivity, and obesity. A recent consensus report indicates strong evidence that physical activity (PA) lowers risk for colon cancer through systemic (i.e., metabolism, inflammation) and obesity reduction pathways. However, despite availability of efficacious behavioral interventions to increase PA among older adults, a critical gap exists between evidence generated and action taken to implement such interventions among AIAN older adults. This gap represents a missed opportunity to implement current evidence-based interventions (EBIs) in cancer prevention among high-risk populations experiencing pronounced CHDs. Implementation science concentrates on understanding and accelerating integration of such EBIs into public health practice settings to improve health and can be leveraged here to address this critical public health gap, thus addressing persistent CHDs and improving overall health among AIAN communities. This F99/K00 Predoctoral to Postdoctoral Fellow Transition Award application assists a promising trainee - Maja Pedersen, who has 15 years of experience in community-based behavioral interventions among rural AIAN communities in the Northern Plains and Alaska regions - to embark on a rigorous research and training program to confront this critical gap using best practices for intervention research with AIAN communities and current implementation science methods. Pedersen?s long-term goal is to become an independent investigator in designing and implementing PA interventions among underserved populations - including AIANs - to improve cancer-related health outcomes and reduce CHDs. Her short-term goals include gaining expertise in the use of multilevel intervention methods, dissemination and implementation science, cancer prevention and control among geriatric populations, experimental design, and intensive longitudinal methods. In collaboration with her multidisciplinary team of predoctoral mentors, she has developed a training plan to initiate these goals via coursework, workshops, scientific meetings, directed readings, and mentored research (F99 Phase). As she transitions into the postdoctoral phase, she will assemble a team of high-level, cancer-focused mentors to support her through continued mentored training with an explicit focus on cancer prevention and control. Her postdoctoral research (K00 Phase) executes the logical next steps in her research sequence on a trajectory toward a full-scale implementation and effectiveness trial as an independent scientist.